We observed over two decades ago that myocardium rendered ischemic, but not irreversibly damaged , exhibited prolonged depression of regional myocardila functrion, long after the complete return of the blood flow and resumption of a normal electrocardiographic pattern. At that time, we did not appreciate the extent to which this characteristic of ischemic myocardium would be involved mechanistically in so many experimental and clinical settings. With the additional work of Kolner and Braunwald, the